Method and system for handling a network-identified emergency session

ABSTRACT

The invention relates to a method and system for establishing an emergency session in a communication system which includes at least one user equipment and one or more network entities involved in establishing an emergency session. When the user equipment initiates a session by sending a message to a network entity indicating an identifier, e.g. the call number or logical name of a called entity, one of said network entities analyses the received identifier. When detecting that the session to be initiated is an emergency session, an information is returned to the user equipment for informing the latter that the initiated session is an emergency session. The user equipment thereupon initiates the execution of an emergency session. Thus, even when the user equipment is unable to detect, by itself, that the intended session is an emergency session, the network will inform the user equipment on the emergency session for ensuring appropriate handling thereof.

FIELD AND BACKGROUND OF THE INVENTION

The invention generally relates to the connection of emergency sessionssuch as emergency calls.

Emergency calls shall be supported in IP Multimedia networks (IMS). TheUE (User Equipment) may usually be able to indicate in the initialsession setup (e.g. in the INVITE message of SIP) that the session is anemergency session.

However, there may be situations where the initial session setup messageis just sent with an ordinary number and there is no indication aboutthe emergency. These situations may e.g. occur when a subscriber isroaming in another IMS network.

It is important to identify the intended emergency session as soon aspossible, because the network and the UE need to perform some specialactions for performing the emergency session.

SUMMARY OF THE INVENTION

The present invention provides method and system for enabling emergencysessions to be established in a reliable manner.

The invention provides a method and/or system as defined in the claims.

This invention discloses means and functions of how the network candetect an emergency session, how the UE can be informed about it andwhat effects this information has on later session setup.

The invention provides among others a Network-identification of anemergency session initiated by a session initiating entity such as auser equipment (UE) including mobile or stationary stations orterminals, or the like.

Even when the user equipment is unable to detect by itself that theinitiated session is an emergency session, it is quickly informedthereon and can then initiate the appropriate steps for establishing theemergency session.

According to a first embodiment of the invention, in order to guaranteeresources at the transport level for the emergency call, a response issent back to the UE immediately after a control means such as P-CSCF hasdiscovered that the session is an emergency session. When the UEreceives such a response it will perform a normal emergency sessionprocedure, e.g. as defined in 3GPP specifications. To execute a normalemergency session, the UE will e.g. obtain or query location informationand send it in the INVITE message and also the UE will activate anemergency PDP context for the session.

The invention enables to identify the session to be an emergency sessionas soon as possible so that the network and the UE can perform thenecessary special actions for the emergency session as quickly aspossible.

In one of the alternative implementations of the invention, the controlentity such as P-CSCF does not respond immediately to UE when it hasreceived an INVITE message from the UE but waits for the reception of amessage, e.g. 183 Session Progress, from an emergency center or anintermediate network entity, and adds to that message the emergencyinformation.

The information about the emergency call is not delayed at all, and thecall establishment is continued in the conventional or any other mannersuch as with the 183 Session Progress message.

Sending an INVITE message takes remarkable radio resources and it is notpreferable to send multiple INVITE messages. Actually there is no delayin session establishment, since UE has not yet started creatingsecondary PDP Context before UE receives the SDP message. This meansthat the indication can be included with high priority for the userplane. If no emergency centre is indicated, a default emergency centermay be chosen.

This invention concerns a situation, in which PDP context activation cannot or will not be performed at first when initiating a session for anyreason, but a message such as an INVITE message is sent first from theUE to the CSCF.

Further details, aspects and advantages of the invention will becomeapparent from the following reference to specific embodiments and theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first embodiment of a method and system in accordancewith the present invention;

FIG. 2 shows a second embodiment of a method and system in accordancewith the present invention;

FIG. 3 illustrates a third embodiment of a method and system inaccordance with the present invention;

FIG. 4 shows an implementation for emergency session processing in anormal case.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

This invention discloses solutions to several problems such as:

-   -   The UE is able to activate an emergency PDP context after it has        been informed about the session characteristics. This is        important to get high priority for the PDP context in the GPRS        (General Packet Radio Service) and RAN (Radio Access Network).    -   The UE sends location information after it is being informed        about the session characteristics (it is assumed that location        information is not sent in every INVITE message). The location        information is used for selecting the most suitable Emergency        Centre (EC).

FIG. 1 shows an embodiment of the invention which includes a calloriginating element, i.e. a session initiating element, such as a mobilestation (UE) 10, and a network which comprises a serving network elementsuch as a Serving GPRS Support Node (SGSN), and a further controlelement such as a Call State Control Function (CSCF) or Proxy Call StateControl Function (P-CSCF) 11. The further network elements necessary forcompleting an IP multimedia session such as a terminating element, agateway node if needed, a subscriber information register such as a homelocation register (HLR) or home subscriber server (HSS), etc. are knownto the skilled man and are therefore neither shown nor described in moredetail. Generally, a MSC (Mobile Switching Centre, not shown) may returnto UE a Call Proceedings message which contains a Priority informationfield defining also EC (Emergency Centre).

In all embodiments described above or below, the UE 1 may be equippedwith a USIM (User Services Identity Module).

The embodiments shown in FIGS. 1, 2, and 3 relate to aNetwork-identified emergency session.

A solution to guarantee resources at the transport level to perform theemergency call is to respond back to the UE 10 immediately after anetwork entity, e.g. a control means such as P-CSCF 11, has discoveredthat the session is an emergency session. When the UE 10 receives theresponse, i.e. is informed, by the network, on the initiated sessionbeing an emergency session, it will perform normal emergency sessionprocedure, e.g. as defined in 3GPP specifications.

FIG. 1 shows the solution at a general level.

-   -   In step 1, the UE 10 sends a session initiation message, e.g. an        INVITE message of SIP (Session Initiation Protocol), which        indicatess an identifier, e.g. the E.164 number or LN (logical        name), of the called entity, to the P-CSCF 11.    -   In a step 2, the P-CSCF 11 analyses the number or LN. When        detecting that a normal session is to initiated, a normal        connection procedure is continued. When, however, the P-CSCF 11        discovers that the call is emergency call, steps 3 to 6 shown in        FIG. 1 are performed.    -   In step 3, a response is sent to the UE 10 indicating that the        session is an emergency session.    -   Step 4: The UE 10 returns an acknowledgement message ACK to the        P-CSCF 11.    -   In an optional step 5, the UE 10 may inform the user that the        session is emergency session, e.g. by displaying an appropriate        message on a display of the UE 10.    -   Then, a normal emergency session is executed (performed) as        indicated by step 6. The execution of a normal emergency session        means that the UE 10 will e.g. obtain location information and        send it in the INVITE message and also that the UE 10 will        activate an emergency PDP context for the session.

The response message at step 3 can be a new message, or an existing SIPmessage or other known message can be used. The information in theresponse message may be a new parameter in SIP protocol, but an existingparameter may also be used.

FIG. 2 shows a solution in which, in step 3, a SIP 302 message “MovedTemporarily” is used as response. The parameter value in the 302 messageindicates that the session is an emergency session. The parameter maye.g. be “Contact: sip:emergency@visited.cscf.com”. This value can e.g.be used in SIP URI when sending a new INVITE message to P-CSCF 11, orthe UE 10 just generates a new INVITE message with the indication of anemergency session. Another alternative can be to use the SIP NOTIFYmethod.

Apart from the above discusion, the embodiment shown in FIG. 2 has thesame structure and functioning as the one of FIG. 1.

FIG. 3 illustrates another embodiment of the invention. In addition tothe UE 10 and the P-CSCF 11, a Serving CSCF (S-CSCF) 12 and an EmergencyCentre (EC) 13 are shown. The embodiment according to FIG. 3 provides analternative functioning as compared to the embodiments of FIGS. 1 and 2.

In order to achieve a very fast session establishment the P-CSCF 11 doesnot respond back to the UE 10 immediately after P-CSCF 11 has discoveredthat the session is an emergency session. On the contrary it continuessession establishment and optionally, if possible, the P-CSCF 11 adds anindication of emergency session to the messages generated by P-CSCF 11for ensuring high priority treatment of the messages.

The details of the procedure are shown in FIG. 3. Taking account of thenature of emergency session it is highly desirable not to add anyadditional delay also in case of abnormal situations to sessionestablishment. By using the alternative of FIG. 3, it is possible toavoid the transfer of another INVITE message over the air interface,which is probably the largest and slowest message and thus verytime-consuming.

The response message (in SIP, preferably a message “183 Progress”) tothe UE 10 preferably includes an indication of emergency session. Thisallows to activate an emergency PDP context for the session.

If there should not exist location information in S-CSCF 12 (or therelevant server) to select an emergency center 13, the S-CSCF 12 (orrelevant server) will select an emergency center 13 without locationinformation of the user (e.g. it selects a default emergency center,nearest emergency center or it may use some other technique to selectthe emergency center e.g. based on the address of P-CSCF 11.

As shown in FIG. 3, in step 1, the UE 10 initiates a sessionestablishment and sends a session setup message, e.g. an INVITE message,to the P-CSCF 11. The P-CSCF 11 analyses the number or logical name (LN)of the called party/entity indicated in the session setup message, anddiscovers that the call is an emergency call. The P-CSCF 11 may add anindication of emergency session to the INVITE message (it is alsopossible that other elements add this indication of emergency session tothe INVITE message).

-   -   In step 2, the INVITE message is forwarded to the S-CSCF 12.    -   In Step 3, the S-CSCF 12 selects an emergency center (EC) 13 and        forwards the INVITE message to the EC 13.    -   Step 4: The EC 13 responds to the INVITE request by returning a        response such as SIP 183 “Session Progress” to the S-CSCF 12.        The subset of the media flows shown in steps 4 to 6 indicates        that messages are returned back to originating endpoints        proposing an EC 13 for providing support, or requesting the        emergency session.    -   Step 5: The S-CSCF 12 forwards the response such as SIP 183        “Session Progress” back to the P-CSCF 11.    -   Step 6: The P-CSCF 11 forwards the response such as SIP 183        “Session Progress” back to the UE 10. The response includes the        indication of emergency session. The UE 10 thus learns that this        session is an emergency session and can act properly.

The circles and ovals shown in FIG. 3 mean “Emergency call detected,Possibility to add an emergency indication”.

FIG. 4 presents a proposal for normal emergency session establishmentfor the case where the UE has USIM. It is assumed that the UE hasactivated a signalling PDP context to the GGSN in the visited PLMN.

In the following, the steps shown in FIG. 4 are described in moredetail, referring to the step numbering of FIG. 4.

-   1. UE may request SAI (Service Area Identity) from SGSN.-   2. SGSN sends response message to UE.-   3. UE sends the SIP INVITE request, containing an initial SDP, to a    P-CSCF determined via the CSCF discovery mechanism. Information    about emergency call is sent in the INVITE message. UE includes the    location information in the INVITE message.-   4. P-CSCF detects that the call is an emergency call using the    information in the INVITE message e.g. by analysing the number or    name requested. P-CSCF selects a S-CSCF in the visited network and    forwards the SIP INVITE request including the information about    emergency call to S-CSCF.-   5. S-CSCF uses the location information to select an appropriate EC.    S-CSCF forwards the request to EC.-   6. The media stream capabilities of the destination are returned    along the signaling path.-   7. S-CSCF forwards the message containing the destination SDP    cababilities to P-CSCF.-   8. P-CSCF authorizes the resources necessary for this session.-   9. P-CSCF forwards the SDP message to the originating endpoint.-   10. UE decides the final set of media streams for this session, and    sends the Final SDP to P-CSCF.-   11. P-CSCF forwards the final SDP to S-CSCF.-   12. S-CSCF forwards this message to EC.-   13. Activate PDP Context Request. The UE activates a PDP context for    the emergency session by sending the Activate Secondary PDP Context    Request message to the SGSN. The UE indicates that the PDP context    is used for an emergency session. For the PDP context, the    Allocation/Retention Priority shall be at once set to the high    value.-   14. The SGSN, when recognising that the PDP context is for an    emergency session, may itself request location information from    SRNC, in order to receive updated or more accurate location    information regarding the UE. SGSN thereafter sends a location    report to Gateway Mobile Location services Centre (GMLC) as    specified in TS 23.271, and the EC may obtain this location    information from GMLC.-   15. Radio Access Bearer Setup-   16. Create PDP Context Request-   17. Create PDP Context Response-   18. Activate PDP Context Accept-   19. UE sends the “Resource Reservation Successful” message to the    terminating endpoint, via the signaling path established by the    INVITE message.-   20. P-CSCF forwards this message to S-CSCF.-   21. S-CSCF forwards this message to EC.-   22. Resources are reserved successfully.-   23. EC sends information about alerting to S-CSCF.-   24. S-CSCF forwards the Ringing message to P-CSCF.-   25. P-CSCF forwards this message to UE.-   26. EC answers the call and sends final 200 OK message to S-CSCF.-   27. S-CSCF forwards final 200 OK message to P-CSCF.-   28. P-CSCF indicates the resources reserved for this session should    now be committed.-   29. P-CSCF forwards final 200 OK message to UE.-   30. UE starts the media flow for this session.-   31. The calling party responds to the 200-OK final response with a    SIP ACK message which is sent to P-CSCF.-   32. P-CSCF forwards the SIP ACK message to S-CSCF-   33. S-CSCF forwards the ACK message to EC.

Although the invention has been described above with reference tospecific embodiments, the scope of protection of the invention intendsto cover all modifications, omissions, additions and amendments of thedisclosed features as well.

The teaching according to the invention is preferably implemented in anAll-IP Network but may also be employed in networks of various othertypes, i.e. in IM, GPRS and UMTS domains.

1. An apparatus, comprising: a receiver configured to receive a messagefrom a user equipment to initiate a session, said message indicating anidentifier of a called entity; an analyzer configured to analyze theidentifier and to detect a request for an initiation of an emergencysession; and a sender configured to send information to the userequipment that the session to be initiated is an emergency session,configured to inform an emergency center or another apparatus that anemergency session is to be established when the session to be initiatedis an emergency session, and to send the information to the userequipment or another apparatus only after receipt of a response from theemergency center.
 2. The apparatus according to claim 1, wherein thereceiver is configured to determine location information of the userequipment, and wherein the sender is configured to send the locationinformation to one of other network elements.
 3. The apparatus accordingto claim 1, wherein the apparatus is configured to initiate an emergencypacket data protocol context for the emergency session.
 4. The apparatusaccording to claim 1, wherein the information sent by the sendercomprises a parameter indicating an address of a network entity to beaddressed for establishing the emergency session.
 5. The apparatusaccording to claim 1, wherein the apparatus comprises a call statecontrol function.
 6. An apparatus, comprising: a receiver configured toreceive a message from a user equipment containing an identifier of acalled entity for initiating a session; an analyzer configured toanalyze the identifier, and to detect that the session to be initiatedis an emergency session; a sender configured to send information to theuser equipment for informing the user equipment that the initiatedsession is an emergency session, wherein the receiver is furtherconfigured to receive a re-initiation message from the user equipment,the re-initiation message comprising the information.
 7. The apparatusaccording to claim 6, wherein the apparatus comprises a proxy-call statecontrol function.
 8. An apparatus, comprising: a sender configured tosend a message to a call controlling network element, said messageindicating an identifier of a called entity; a receiver configured toreceive, from the call controlling network element, informationindicating that an emergency session is being initiated, wherein theapparatus is configured to re-initiate the session by sending a messageto the call controlling network element, the message comprising theinformation.
 9. The apparatus as recited in claim 8, configured to atleast one of: initiate the emergency session using a packet dataprotocol context, be a user equipment.
 10. The apparatus according toclaim 8, wherein the information in the message sent to the networkelement comprises a parameter indicating an address of a network entityto be addressed for establishing the emergency session.
 11. Anapparatus, comprising: a sender configured to send a message to anetwork entity to initiate a session, the message indicating anidentifier of a called entity; a receiver configured to receive, whenthe session to be initiated is an emergency session, an informationinforming the apparatus that the initiated session is an emergencysession; and an initiator configured to initiate execution of anemergency session upon receipt of said information.
 12. The apparatusaccording to claim 11, wherein the initiator further comprises anobtainer configured to obtain location information of the apparatus, andto send the location information to a network entity.
 13. The apparatusaccording to claim 11, wherein the transmitter is configured to send themessage including a parameter indicating an address of a network entityto be addressed for establishing an emergency session.
 14. The apparatusaccording to claim 11, wherein the sender is configured to send anacknowledgement message to a call controlling network element inresponse to the receiver receiving the information informing theapparatus that the initiated session is an emergency session.
 15. Theapparatus according to claim 11, wherein the initiator is configured toexecute a new emergency session upon receipt of the information, whereinthe new emergency session is configured to provide additional networkresources for an emergency call.
 16. An apparatus, comprising: a senderconfigured to send a message to a network entity for initiating asession, the message indicating an identifier of a call entity; areceiver configured to receive, when the session to be initiated is anemergency session, information informing the apparatus that theinitiated session is the emergency session; and a sender configured tosend an acknowledgement message to a call controlling network element inresponse to receiving the information informing the apparatus that theinitiated session is an emergency session.
 17. The apparatus accordingto claim 16, wherein the emergency session is initiated using a packetdata protocol context.
 18. A method, comprising: sending a message to acall controlling network element, said message indicating an identifierof a called entity; receiving, from the call controlling networkelement, information indicating that an emergency session is beinginitiated; and re-initiating the session by sending a message to thecall controlling network element, the message comprising theinformation.
 19. The method as recited in claim 18, wherein theemergency session is initiated using a packet data protocol context. 20.The method according to claim 18, wherein the information in the messagesent to the network element comprises a parameter indicating an addressof a network entity to be addressed for establishing the emergencysession.
 21. A method, comprising: sending a message to a network entityto initiate a session, the message indicating an identifier of a calledentity; receiving, when the session to be initiated is an emergencysession, an information informing the user equipment that the initiatedsession is an emergency session; and initiating execution of anemergency session upon receipt of said information.
 22. The methodaccording to claim 21, further comprising: obtaining locationinformation of the user equipment; and sending the location informationto a network entity.
 23. The method according to claim 21, wherein saidsending comprises sending the message comprising a parameter indicatingan address of a network entity to be addressed for establishing anemergency session.
 24. The method according to claim 21, furthercomprising: sending an acknowledgement message to a call controllingnetwork element in response to receiving the information regarding theinitiated session is an emergency session.
 25. The method according toin claim 21, further comprising: executing a new emergency session uponreceipt of the information, wherein the new emergency session isconfigured to provide additional network resources for an emergencycall.
 26. A method, comprising: sending a message to a network entityfor initiating a session, the message indicating an identifier of a callentity; receiving, when the session to be initiated is an emergencysession, information informing a user equipment that the initiatedsession is the emergency session; and sending an acknowledgement messageto a call controlling network element in response to receiving theinformation informing the user equipment that the initiated session isan emergency session.
 27. The method according to claim 26, wherein theemergency session is initiated using a packet data protocol context.